Apparatus for flowing and filling liquified inert gas

ABSTRACT

An apparatus for flowing and filling liquified gases, which fuctions to flow and to fill liquified bases into cans from a liquified gas storage tank immediately before seaming of the cans. The apparatus includes a solenoid for attracting an upper portion of a needle of a flow valve formed from a needle valve to open and clode the valve. A pulse motor adjusts an opening-degree of the valve. A valve opening-degree detecting device detects the opening degree. A direction changing nozzle is formed with a nozzle opening obliquely descended in a direction of transporting a can, below the flow valve. A line speed and a balve open amount in a high speed region and a low speed region are respectively set to thereby obtain a line speed/valve opening-degree conversion table, on the basis of which an opening-degree of the valve can be controlled following the line speed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an apparatus for flowing and filling liquefiedinert gas. The apparatus functions to flow and to fill a liquefied inertgas, such as a liquid nitrogen, immediately before seaming of a can inorder to apply internal pressure to the can.

2. Description of the Prior Art

In the past, for obtaining an internal pressure of a can formed of asoft material, a liquefied inert gas (hereinafter merely referred to asthe liquefied gas) such as liquid nitrogen has been filled into a headspace of a can filled with liquid immediately before seaming of the can.The internal pressure of the can varies with a difference of a fillingamount of the liquefied gas such that if the filling amount is small,the internal pressure is insufficient resulting in an insufficientstrength of the can. Conversely, if the filling amount is large,over-pressure results. It has been therefore required that the fillingamount is always controlled to a proper value according to the seamingcondition and the like.

In the past, filling of the liquefied gas into a can in a high-speedcanning line has been carried out in such a manner that the liquefiedgas is continuously made to flow into cans continuously conveyed by aconveyor from a liquefied gas storage tank. The filling amount iscontrolled by changing an opening degree of a valve. As for the methodfor controlling the filling amount, a method has been proposed in whichan opening degree of a valve is controlled to follow the line speed (forexample, Japanese Patent Application Laid-Open Nos. 146797/1983 and166196/1983).

In the flow-amount control devices heretofore proposed, a valve rod of aneedle valve is always urged by a spring in a direction of opening thevalve (upward). An upper end of the valve rod is defined by a drive rodmoved up and down by means of a pinion rack mechanism or anelectrically-driven cylinder. The drive rod is displaced according tothe line speed to thereby control the opening of the valve at the sametime when the valve is opened. The opening degree of the valve withrespect to the line speed is obtained by inputting into a microprocessorin advance, a conversion table which has calculated, using internalpressure of a can as a parameter, the relationship between the linespeed and the flow amount of liquid nitrogen required to obtain a fixedinternal pressure, and effecting arithmetic operation on the basis ofthe conversion table corresponding to the detection valve of the linespeed. The liquefied gases from the valve, which are filled into thecans, are stored in a sintered metal container to de-energize them.Scattering of the liquefied gases outside the can is prevented toimprove the yield of the liquefied gases into the can.

However, in the above-described conventional apparatus, even if theopening degree of the valve is varied to follow the speed of the line,if a flow of liquid is received by a porous container a problem arisesin that the response is so slow as to make it difficult to properlycontrol the flow amount of the liquefied gases to follow the line speed.

Furthermore, in the above-described conventional apparatus, since thecontrol for the opening and closing of the valve and the control of theopening degree are carried out by one and the same means, it isdifficult to control the opening degree of the valve properlyparticularly in the early stage of operation. That is, at the start ofoperation of a seamer, normally, rolling of a can starts after idleoperation. Therefore, in the case of a high-speed operation, cans areabruptly conveyed to the flow-down position. Thus, the opening degree ofthe valve needs to be set while comparing the operation of opening thevalve, the opening degree of the valve during the opening and the valueof the opening degree of the valve obtained by the arithmetic operationfrom the line speed. Therefore, the control of the opening degree of thevalve is late, failing to obtain an accurate opening degree of thevalve. As a result, cans can be produced which are defective in internalpressure in the early stages of the operation. In the above-describedprior art, the flow amount is controlled on the basis of the specificconversion table of the line speed/the open amount of valve set for highspeed and for low speed. However, the proper amount of the liquefiedgases filled into the cans differs with various conditions such as theamount of the contents , filling conditions therefore, and the like. Ithas been difficult to obtain a proper filling amount corresponding tothe change in all these conditions merely by using a specific conversiontable.

On the other hand, an arrangement it has been proposed wherein a devicefor opening and closing a flow valve and a device for controlling anopening degree of a valve are independently organized. In order toclosely control the flow amount corresponding to the change in variousconditions such as a filling condition for cans, a seaming condition andthe like, the inclination and offset thereof are selected correspondingto the change in the conditions to obtain an optimum conversion tablewhich meets the conditions. The flow amount is controlled on the basisthereof to thereby overcome the problems noted above (Japanese PatentPublication No. 50200/1986). In this case, selection of thespeed/opening degree conversion table according to the conditions iscarried out by two units, i.e., a gain setting unit for determining aninclination and an offset setting unit for moving the table in parallel.Therefore, for example, in the case where a conversion table with onlyan opening degree at a low speed changed is desired to be obtained, theinclination is first changed by the gain setting unit, and two settingunits had to be changed. Further, to insure whether the set is corrector not, it has been necessary to switch the low-speed operation and highspeed operation to confirm an opening degree. Moreover, when a flow ofliquefied gases flowing from the flow valve is directly introduced intocans, scattering increases. When a porous receiving container isprovided halfway in the flow in order to overcome such a scattering,there poses a problem in that the response to the line speed isdeteriorated.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus forflowing and filling liquefied gases, which can accurately control a flowamount of liquefied gases into a can in order to obtain a fixed internalpressure within the can according to a line speed. The apparatus canobtain a high speed response of a flow valve with respect to a variationin line speed even at the start of flow and at the stop of flow.

It is a further object of the present invention to provide an apparatusfor flowing and filling liquefied gases, which can guide a flow ofliquid flowing from a flow valve to a liquid level, relieving a shockwhen the flow of liquid reaches the liquid level within the can withoutimpairing the response to the line speed, to fill the liquefied gaseswith good yield.

It is another object of the present invention to provide an apparatusfor flowing and filling liquefied gases which can easily and positivelychange a speed/opening degree conversion table corresponding to thechange in conditions.

For achieving the above-described objects, the present inventionprovides an apparatus for flowing and filling liquefied gases, whichfunctions to flow and fill the liquefied gases within a liquefied gasstorage tank into a can immediately before seaming of the can. A flowvalve is in the form of a needle valve. The valve is controlled by asolenoid for attracting an upper portion of a needle to open and closethe flow valve. A pulse motor adjusts an opening degree of the flowvalve. A valve opening-degree detection device detects an opening degreeof the flow valve. A direction change nozzle, formed with a nozzleorifice obliquely descended in a direction of transporting the can, isprovided below the flow valve to impart a speed component in a directionof transporting a can to a flow of liquefied gases flowing from astorage tank, thus preventing scattering of liquefied gases outside thecan.

The apparatus further comprises a line speed detector for detecting aline speed, a speed setting unit and a valve opening-degree setting unitfor a high speed region and a low speed region. The valve opening-degreesetting unit sets a line speed/valve opening-degree conversion tablewith respect to the line speed. A device is provided for arithmeticallyoperating an opening degree of a valve by a line speed detection valueon the basis of the conversion table. Also provided is a device forcomparing the arithmetically operated value with the valveopening-degree detection value. The opening degree of the valve can becontrolled to follow the change in speed of the line, and therelationship between the line speed and the valve opening degree can beeasily changed according to the change in the filling condition.

In the apparatus of the present invention constructed as describedabove, according to the speed/opening degree conversion table forconverting the line speed into the valve opening degree, if a speed in ahigh speed region and an opening degree at that time, and a speed in alow speed region and an opening degree at that time are set as shown inFIG. 4(a), a speed/opening-degree conversion graph is obtained and aspeed/opening-degree conversion table as desired can be prepared. Forexample, for changing only the opening degree at the low speed, aconversion table as desired can be simply obtained merely by changingthe set value of a low speed opening-degree setting unit as shown inFIG. 4(b). The opening degree of the valve is controlled following theline speed on the basis of the thus set conversion table. The openingdegree of the valve is arithmetically operated from the line speeddetection valve whereby the valve opending-degree adjusting device iscontrolled independently of the valve opening and closing device.Accordingly, at the beginning of operation, the valve opening-degreeadjusting device is controlled to follow the line speed simultaneouslywith the start of operation. When a can is then detected by a candetector, the valve opening and closing device actuates to open thevalve. Since at that time, the valve opening-degree adjusting device isadjusted to a fixed position according to the speed, a proper openingdegree of a valve is obtained at the start of operation. The flow ofliquefied gases from the flow valve is applied with a speed component ina direction of transporting a can by a direction changing nozzle,whereby a shock produced when reaching a liquid level in the can isrelieved, scattering outside the can is prevented and an amount ofliquefied gases proportional to an open amount of the valve is filled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front sectional view of an embodiment of an apparatus forflowing liquefied gases according to the present invention;

FIG. 2 shows an arrangement of a liquefied gas filling line;

FIG. 3 is a block diagram of a control apparatus according to thepresent invention;

FIGS. 4 (a) and (b) are respectively explanatory views showing a methodfor setting a speed/opening-degree conversion graph according to thepresent invention;

FIG. 5 is a speed/opening-degree conversion graph showing an example forsetting an undulation absorbing width according to the presentinvention;

FIG. 6 is a graph showing the relationship between the line speed andthe opening degree of the valve; and

FIG. 7 is a flow chart of an embodiment according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows one example of an apparatus for flowing liquefied gases towhich the present invention is applied. In FIG. 1, reference numeral 1designates a body of a liquefied gas storage tank. The liquefied gasesare introduced into the tank from a bomb (not shown) and stored therein.The liquefied gases are made to flow down from a valve device 2 providedon the bottom and filled into cans C continuously transported by aconveyor 3. The valve device 2 has a valve seat 4 and a needle 6, fittedin a tapered portion of a valve opening 5 of the valve seat, to effectopening and closing of the valve and adjustment of an opening degree. Anupper end of the needle 6 is connected to a plunger 7 of a solenoid 8which is a means for opening and closing the valve. The plunger 7 isattracted by the operation of the solenoid 8 to open the valve. In theplunger stroke of the solenoid 8 is positioned a valve opening-degreecontrol rod 9 for defining a stroke of the plunger 7. The opening-degreecontrol rod 9 is controlled in its position by a pulse motor 10 tocontrol the opening degree of the valve to follow the line speed. Theamount of movement of the opening-degree control rod 9 is alwaysdetected by a potentiometer 22 which is a valve opening-degree detector.

Reference numeral 11 designates a direction changing nozzle forobliquely guiding a flow of liquefied gases flowing down from aliquefied gas flow valve. The direction changing nozzle 11 has a nozzleorifice 12 inclined in a direction of transporting the can C. The flowof liquefied gases flowing down from the flow valve flows down throughthe nozzle orifice 12 thereby imparting a speed component in a directionof transporting the can to relieve the shock produced when reaching aliquid level of the can C and prevent scattering of the liquefied gasesoutside of the can. The nozzle orifice 12 is in the shape of a V or adiamondshape which is large enough with respect to the flow amount andis converged into a single streak without diffusion of the flow liquid,and the average effect resulting from the downwardly inclined surfacemay be obtained. A heater 13 is provided to prevent a flow turbulenceresulting from generation of frost at the nozzle orifice 12.

FIG. 2 shows a liquefied gas filling line to which the liquefied gasflow apparatus is applied. In FIG. 2, a filling machine 14 fills thecontent liquids into the can. The liquefied gas flowing apparatus isshown as numeral 15 and a seamer is shown as 17. The can is filled withthe content liquid by the filling machine 14. The liquified gas is addedto the head space by the liquefied gas flow apparatus 15 while beingtransported to the seamer 17 by means of a conveyor. A can lid issupplied to an opening by a can-lid turret 16 and the seaming of the canlid is carried out by seamer 17.

The control method for the aforementioned liquefied gas flowingapparatus will be described hereinafter.

FIG. 3 is a block diagram of control apparatus. The control apparatuscomprises a detection unit, a condition setting unit, a centralprocessing unit and a control output unit. Data for conversion of a linespeed to a valve opening amount and control program are stored in thecentral processing unit CPU.

The detection unit comprises a speed converter, a seamer stop detector,a can detection sensor 20 and a valve opening-degree detector, which areconnected to an input port of the CPU. In the speed converter, a cam topof a speed detection cam 18 provided on a drive shaft of a can-lidsupply turret 16, shown in FIG. 2, is detected by a speed detectionsensor 19, the detection signal being converted into a line speed. Theseamer stop detecting unit detects the stop of a seamer 17 by notreceiving a detection signal for a fixed period of time from the speeddetection sensor 19. The speed detection cam 18 is not necessarilyprovided on the drive shaft of the can-lid supply turret 16 but may beprovided on another drive shaft. The seamer stop signal does not dependon the output of the speed detection sensor 19 but an operating signalfor the seamer 17 may be introduced from a seamer control panel.

The condition setting unit comprises a table preparation data settingunit comprising a speed setting unit and an opening-degree setting unitfor high speed, a speed setting unit and an opening-degree setting unitfor low speed, and setting unit for an undulation absorbing width, and acontrol parameter setting unit comprising an instantaneous value controland setting unit and an average number setting unit. The conditionsetting unit is connected to an input port of the CPU. The line speedalways varies finely due to variations of the load of the seamer 17, andthe like, as shown in FIG. 6, and also has a long periodic undulation.The measured value always varies due to an error in construction of acam top of the speed detection cam 18 and the like. When the openingdegree of the valve is controlled accurately to follow the finevariation in speed a deterioration in the service life of apotentiometer 22 of the opening-degree detector and the opening-degreeadjusting means occurs. However, it has been proven from experimentsconducted by the present inventor that if variation in measuring speedis within a fixed range, a problem will not occur even if the openingdegree of the valve is not accurately followed. In view of the aforesaidfact, in the present embodiment, the opening degree of the valve is madeconstant with respect to the speed variation within a fixed range so asto protect the valve opening-degree detector and the valveopening-degree setting means. The aforementioned setting unit for aninstantaneous value control and the average number setting unit areprovided to set the control parameter therefor. Since the error in thecam top can be absorbed by taking an average with integer times of thenumber of tops of a cam, control can be effected at the speed of theaverage value. However, if control with an average value is alwayseffected, the followability when the seamer 17 is varied in speed isinsufficient. It is therefore designed so that when a difference betweenthe average speed and the instantaneous speed exceeds a fixed value, theopening degree of the valve is made to be varied for each can. Theaforementioned instantaneous value control and setting unit is providedto set a threshold in the variation range when shifting to control aninstantaneous value. The average number setting unit is provided to setthe average number used in control of the average value.

On the other hand, the setting unit for undulation absorbing width isprovided to set the range by making an opening of a fixed portionconstant in a high speed region of a speed/opening degree conversiontable to absorb the undulation of a seamer speed.

Influence of variation in measuring speed on variation in valveopening-degree is greater at the time of high speed. For example, incase of 600 cpm (cans per minute), if the number of pulses passingthrough a can is 500 pulses, the number of pulses passing through a canat a high speed of 1200 cpm is 200 pulses. Accordingly, in the casewhere variation by one pulse is present, at the time of low speed,variation is 1/500 whereas at the time of high speed, it is 1/250. Atthe time of high speed, even for a minute variation, the control of thevalve opening-degree immediately responds. However, in the high speedregion, even if the valve opening degree is made constant with respectto variation in speed in the fixed range, variation in internal pressureof the can, can be ignored. For example, as shown in FIG. 5, where a canhas a standard internal pressure, 1.8 Kg/cm², a value of 1200 cpm±20 cpmis set to be constant. Thus, the internal pressure at 1180 cpm is 1.85Kg/cm² and the internal pressure at 1220 cpm is 1.75 Kg/cm². Thedifference therebetween is merely 0.05 Kg/cm², which is an amount thatmay be ignored when compared with an unevenness ±0.5 Kg/cm² of theinternal pressure in general filling of liquid nitrogen. On the basis ofthe aforementioned knowledge, the present invention has intended toprolong the service life of the valve opening-degree control apparatusby making the opening degree constant in a fixed range of the high speedregion of the speed/opening-degree conversion table as shown in FIG. 5.The aforesaid fixed range can be set under the optimum condition bymaking suitable presetting possible. The relationship between the linespeed and the valve opening-degree according to the aforementionedcontrol method is shown in FIG. 6.

The control output unit comprises a pulse motor 10 for changing anopening degree and an opening-degree indicator. The control output unitis connected to an output port of the CPU.

Control of flowing of liquefied gases in the apparatus for fillingliquefied gases organized as described above is carried out as follows:

In the case where the line speed is high, such as 1200 cpm, a fixed linespeed is set by a speed setting unit for high speed, and an amount ofthe valve opening-degree at the speed is set by an opening-degreesetting unit in consideration of the filling condition or the like. Theundulation absorbing width at the speed region is set by the settingunit for an undulation absorbing width and input into the CPU. In theCPU, a speed/valve opening conversion table is prepared on the basis ofthese inputs. In the case where the line speed is in a region of lowspeed, such as 600 cpm, table preparing data is input by the speedsetting unit and opening-degree setting unit for low speed.

Next, as a control parameter, a difference between the average speed andinstantaneous speed shifting to control an instantaneous value is inputto the setting unit for an instantaneous value control, and an averagenumber used for control of an average value is input to the averagevalue setting unit and input into the CPU.

In this manner, when the condition setting unit is provided and aprogram is started, a pulse is generated every detection of a cam top bythe speed detection sensor 19, and the pulse width is counted by a shortpulse produced by the speed converter to thereby convert it into a linespeed which is read in the CPU. At that time, when the speed detectionsensor 19 does not produce pulses for a predetermine period of time, aseamer stop signal is input from the seamer stop detection unit, as aconsequence of which the valve is closed. Accordingly, when the seamerstops, due to the occurrence of jamming, in the state wherein a can ispresent, the flow of the liquefied gases momentarily stops, thuspreventing a waste of the liquefied gases and occurrence of defectivecans. It is noted that the seamer stop signal can be directly input fromthe control panel for the seamer.

A speed detection signal is read whereby a valve opening-degree isarithmetically determined based upon the line speed/valve opening-degreeconversion table. A control signal is output to the pulse motor 10 forchanging an opening-degree compared with a signal from the valveopening-degree detector to control a position of the opening degreecontrol rod 9 and set the valve opening-degree. When a can-presentsignal is provided from the can detection sensor 20, the solenoid 8 isactuated to immediately open the valve. Since the valve opening andclosing means and the valve opening-degree adjusting means aredependently provided so as to independently control the valve openingdegree, accurate valve opening-degree can be obtained even in the earlystage of operation.

The above-described control flow is shown in a flow chart in FIG. 7.

As described above, the valve opening-degree is controlled to follow thespeed of the line, and the liquefied gases flows down from the valve.The liquefied gases from the valve is applied with a speed component ina direction of transporting a can by the direction changing nozzle 11and filled into cans moving thereunder. The speed component in adirection of transporting a can is applied to the flow of liquefiedgases to thereby relieve the shock produced when reaching a liquid levelin the can. Scattering of liquid can be satisfactorily prevented withoutthe provision of a porous tray in the midst portion as in prior art.Since the tray is not provided, the change in the valve opening-degreedirectly serves as the change in the filling amount in the can, thusproviding the high speed followability when the valve opening-degree ischanged.

What is claimed is:
 1. An apparatus for flowing liquefied gases from aliquefied gas storage tank for filling liquefied gases into cans, on aconveyor system, immediately before seaming of said cans, said apparatuscomprising:a valve device including a valve opening, formed in a bottomsurface of a liquefied gas storage tank, and a needle fitted into saidvalve opening; a valve device actuating solenoid having a plungerconnected to an upper portion of said needle, said valve deviceactuating solenoid moving said needle upward and downward by attractingor releasing said plunger to open and close said valve opening; a valvecontrol rod which defines a stroke of said plunger; a pulse motor formoving upward and downward said valve control rod to adjust an openingamount of said valve device; a valve opening-degree detection means fordetecting a position of said valve control rod to detect an openingdegree of the valve device; a line speed detector for detecting a linespeed of said cans on a conveyor system and for generating a line speedsignal; and a control device for controlling an opening-degree of saidvalve device in response to said line speed signal from said line speeddetector, said control device includinga central processing unit, andhigh and low speed setting units and high and low valve opening-degreesetting units in a paired relation for operating in a high line speedregion and a low line speed region, said speed and valve opening-degreesetting units inputting to said central processing unit a linespeed/valve opening-degree conversion table for determining a valveopening-degree with respect to the line speed in a relationship whichvaries according to whether the line speed is in said high line speedregion or said low line speed region, wherein based upon said conversiontable input by said speed setting units and said valve opening-degreesetting units, an opening amount of said valve device is calculated bysaid central processing unit from a detected value of said line speedfrom said line speed detector, and said central processing unit comparesa calculated opening amount with a detected value of said valveopening-degree detected by said valve opening-degree detection means,and said central processing unit inputting a drive signal to said pulsemotor until said calculated value and said detected value coincide. 2.An apparatus for flowing liquefied gases from a liquefied gas storagetank for filling liquefied gas into cans, on a conveyor, immediatelybefore seaming of said cans, said apparatus comprising:a valve deviceincluding a valve opening, formed in a bottom surface of a liquefied gasstorage tank, and a needle fitted into said valve opening; a valvedevice actuating solenoid having a plunger connected to an upper portionof said needle, said valve device actuating solenoid moving said needleupward and downward by attracting or releasing said plunger to open andclose said valve opening; a valve control rod which defines a stroke ofsaid plunger; a pulse motor for moving upward and downward said valvecontrol rod to adjust an opening amount of said valve device; a valveopening-degree detection means for detecting a position of said valvecontrol rod to detect an opening degree of the valve device; a linespeed detector for detecting a line speed of said cans on a conveyor andfor generating a line speed signal; and a control device for controllingan opening-degree of said valve device in response to said line speedsignal from said line speed detector, said control device includingacentral processing unit, high and low speed setting units and high andlow valve opening-degree setting units in a paired relation foroperating in a high line speed region and a low line speed region, saidspeed setting units inputting to said valve opening-degree setting unitsinputting to the central processing unit a line speed/valveopening-degree conversion table for determining a valve opening-degreewith respect to the line speed in a relationship which varies accordingto whether the line speed is in said high line speed region or said lowline speed region, p2 an instantaneous value control setting unitinputting to said central processing unit a speed variation range forcontrolling the opening degree of the valve device in response to aninstantaneous speed of the line speed detected by said line speeddetector, and an average number setting unit inputting to the centralprocessing unit an average line speed in which an opening degree of thevalve device is constant with respect to a variation in line speedwithin a given range of line speeds; and wherein aid control processingunit compares said line speed detected by said line speed detector withsaid average line speed of said average number setting unit, and anamount of opening degree of said valve device is calculated by saidcentral processing unit based upon said conversion table of said speedsetting unit and said valve opening-degree setting unit from a linespeed set by either (a) said average number setting units, if adifference between said line speed and said average line speed is withinsaid speed variation range set by said instantaneous value setting unitor (b) a detected value of line speed from said line speed detector, ifa difference is outside the speed variation range, said centralprocessing unit comparing said calculated value within the detectedvalue of the valve opening-degree detected by said valve opening-degreedetection means, and said central processing unit inputting a drivesignal to said pulse motor until said calculated value and said detectedvalue coincide.